1. Field of the Invention
The present invention relates to a light-emitting diode (LED) indicator lamp that uses LEDs as its light source and is used as, for instance, a warning lamp.
2. Prior Art
Indicator lamps that use LED light sources have long been a preferred choice as illuminating devices such as status and warning lights. The reasons for this include the fact that they do not require frequent replacement of the light source, as do candescent lamps, nor are they vulnerable to shock and vibration. In particular, lamps that use LEDs as their light source are currently used extensively at entrances and exits, and at construction sites, etc. where safety is a concern.
However, since the amount of light given off by an LED is small, in prior art LED indicator lamps, a large number of LEDs are installed on, for instance, a circuit board, and the circuit board is set in the center of the globe (which is an illuminating surface of the lamp) so that light from the LEDs is emitted outward from the center of the globe toward its circumference. Nonetheless, the distance between the LEDs and the circumference of the globe is short; as a result, the light from the LEDs reaches the globe before it is adequately diffused. Thus, it appears to an observer as a grainy light source; and even though a large number of LEDs are used, it is not possible to make efficient use of their emitted light.
One approach to solve this problem is to use a reflecting means so as to diffuse the light. For instance Japanese Utility Model Application Laid-Open (Kokai) No. S62-78770 discloses an hourglass-shaped reflector, and Japanese Utility Model Application Laid-Open (Kokai) No. S63-176214 teaches a reflecting mirror formed as a paraboloid of rotation.
In these prior arts, however, the light is emitted so that it has an appearance of a grainy or striped light source, which in fact degrades visibility. So as to obtain an adequate light emission from the LEDs, Japanese Registered Utility Model No. 2568899 discloses a lamp with a conical reflecting surface. However, this lamp has some problems. Due to the demanded reflection efficiency, the brightness is poor compared to that obtained with a direct light. Also, since the reflecting means is installed in the globe (indicator) for diffusing the light emitted from the LEDs, the manufacturing costs increase significantly, and the overall size of the globe also increases.
Accordingly, the present invention is to solve the above-described problems of the prior art.
The object of the present invention to solve problems associated with the installation of LEDs in the center of a globe and problems associated with the use of a reflecting means, thus providing a light-emitting diode indicator lamp that makes more efficient use of the light emitted from the installed LEDs.
Another object of the present invention is to solve the above problems of the prior art by configurations that can improve the efficiency of diffused light emitted from the LEDs, while at the same time simplifying the structure, thus achieving a cost reduction.
More specifically, the present invention is a light-emitting diode indicator lamp which comprises an indicator globe or indicator globes arranged one on the other in stages and a plurality of light emitting diodes (LEDs) installed in the globe(s) as a light source, and the plurality of light-emitting diodes are disposed at prescribed intervals on or near the inner circumferential surface of the globe(s) so that the diffusing light from each one of the LEDs travels toward an area on the inner circumferential surface of the globe that is diametrically opposite from such each one of the light-emitting LEDs.
Since the light emitted by a light source, which is an LED and disposed in the inner circumferential surface of a globe(s), travels toward locations on the opposite side (or the facing surface) of the glove, a sufficient distance for the light to spread out can be obtained, and a uniform light distribution is obtained. Since no reflecting means is installed in the light path, the light does not attenuate, resulting in more efficient use of the LEDs and a conservation of power.
Furthermore, since no reflecting means is used, it is possible to reduce cost; and since there are fewer components to be used, it is possible to improve reliability.
In the present invention, LEDs are provided on or near the inner circumferential surface of the globe, and these light-emitting diodes can be mounted on a ring-shaped base provided around the inner circumferential surface of the globe. Thus, the installation of the LEDs in the indicator lamp is greatly simplified.
In addition, the ring-shaped base can be a rib that is formed as an integral part of the globe and disposed on the inner circumferential surface of the globe. In this case, by way of integrally forming the rib in the globe by a synthetic resin as a ring-shaped mounting base, only needs to install the LEDs in the proper portions of the rib. Thus, the installation of the LEDs is very simple.
Furthermore, the ring-shaped base can be a narrow plate that is installed around the inner circumferential surface of the globe. With this narrow plate type base, the LEDs are installed in advance on the base, and then such a base with the LEDs thereon is installed in the globe by simply mounting the base around the inner circumferential surface of the globe. The narrow plate can be a printed circuit board (PCB), and this can further simplify the structure.
Furthermore, the ring-shaped base can be a cylinder formed from sheeting or film to be installed around the inner circumference of the globe. With this structure, the LEDs are provided in a cylinder made of light-weight sheeting or film, and it can reduce the weight and cost of the overall indicator lamp.
In addition, the ring-shaped base can be obtained by joining a plurality of frames together into a ring shape. With this ring-shape frame, it is possible to reduce the weight and cost of the indicator lamp as in the case of a sheeting or film ring-shaped base. Further, the void-to-solid ratio for the light emitted by the LEDs is improved, and there will be less components that block the light.
Furthermore, the light-emitting diode indicator lamp can be obtained with a wire installed around the inner circumferential surface of the globe. The use of wire as the ring-shaped base can provide an even greater weight and cost reduction and further improvement in void-to-solid ratio.
In the present invention, the LEDs are directly disposed in the globe circumferential surface or on a ring-shaped base provided inside the globe. However, in the present invention, the light-emitting diodes can be provided on a connecting member that is connected to a shade plate of the globe and located near at the inner circumference of the globe. With this structure, the LEDs can either be mounted on a connecting member suspended downward from an upper shade plate or on a connecting member extending upward from a lower shade plate. This provides a major advantage in that the mounting of the LEDs on the shade plates can be done during fabrication of the shade plates. Thus, the task of mounting the LEDs in the globe can be greatly simplified.
Furthermore, in the present invention, the LEDs emit light directly or straight toward (normal to) a facing area of the inner circumference of the globe; however, the LEDs can be disposed so as to emit light in an oblique direction. With this arrangement, an oblique emission of light can be realized, and this is advantageous in terms of changing the directivity of the emitted light.
Furthermore, in the present invention, not only can the globe be made so that it transmits light emitted by the LEDs to the outside, but the globe can be formed as a liquid crystal display (LCD) panel. With this LCD panel globe, the light from the LEDs is used as a backlight for an LCD display for displaying text, symbols and graphics (i.e., information to be conveyed to an observer). Thus, the globe can be used as an indicator having another function than a lamp that merely emits lights.